Leduc Guillaume, Vidal Laurence, Tachikawa Kazuyo, Rostek Frauke, Sonzogni Corinne, Beaufort Luc, Bard Edouard
CEREGE, UMR6635, CNRS Université Paul Cézanne Aix-Marseille III, Collège de France, Europôle de l'Arbois, BP 80, 13545 Aix-en-Provence Cedex 04, France.
Nature. 2007 Feb 22;445(7130):908-11. doi: 10.1038/nature05578.
Moisture transport from the Atlantic to the Pacific ocean across Central America leads to relatively high salinities in the North Atlantic Ocean and contributes to the formation of North Atlantic Deep Water. This deep water formation varied strongly between Dansgaard/Oeschger interstadials and Heinrich events-millennial-scale abrupt warm and cold events, respectively, during the last glacial period. Increases in the moisture transport across Central America have been proposed to coincide with northerly shifts of the Intertropical Convergence Zone and with Dansgaard/Oeschger interstadials, with opposite changes for Heinrich events. Here we reconstruct sea surface salinities in the eastern equatorial Pacific Ocean over the past 90,000 years by comparing palaeotemperature estimates from alkenones and Mg/Ca ratios with foraminiferal oxygen isotope ratios that vary with both temperature and salinity. We detect millennial-scale fluctuations of sea surface salinities in the eastern equatorial Pacific Ocean of up to two to four practical salinity units. High salinities are associated with the southward migration of the tropical Atlantic Intertropical Convergence Zone, coinciding with Heinrich events and with Greenland stadials. The amplitudes of these salinity variations are significantly larger on the Pacific side of the Panama isthmus, as inferred from a comparison of our data with a palaeoclimate record from the Caribbean basin. We conclude that millennial-scale fluctuations of moisture transport constitute an important feedback mechanism for abrupt climate changes, modulating the North Atlantic freshwater budget and hence North Atlantic Deep Water formation.
水汽从大西洋经中美洲输送到太平洋，导致北大西洋盐度相对较高，并促使北大西洋深层水形成。在上一个冰期期间，这种深层水形成在丹斯加德/厄施格尔间冰阶和 Heinrich 事件（分别为千年尺度的突然变暖事件和变冷事件）之间变化很大。有人提出，跨中美洲的水汽输送增加与热带辐合带向北移动以及丹斯加德/厄施格尔间冰阶同时发生，而 Heinrich 事件则相反。在这里，我们通过比较来自烯酮和 Mg/Ca 比值的古温度估计值与随温度和盐度变化的有孔虫氧同位素比值，重建了过去 9 万年赤道东太平洋的海面盐度。我们检测到赤道东太平洋海面盐度有高达两到四个实用盐度单位的千年尺度波动。高盐度与热带大西洋热带辐合带向南迁移有关，与 Heinrich 事件和格陵兰冰期同时发生。根据我们的数据与加勒比海盆古气候记录的比较推断，巴拿马地峡太平洋一侧这些盐度变化的幅度明显更大。我们得出结论，水汽输送的千年尺度波动构成了突然气候变化的重要反馈机制，调节着北大西洋淡水收支，进而影响北大西洋深层水的形成。
